This invention relates to an apparatus for amorphous bonding of tubulars.
During the construction of oil and gas wells it is usual to connect a large number of tubulars. Conventionally this is effected by screw couplings. One of the disadvantages of this construction is that the couplings are prone to corrosion with the result that a whole string of tubulars may have to be replaced every few years, particularly in high temperature, high pressure wells containing corrosive vapours.
It has been suggested that the longevity of such tubulars could be greatly increased, perhaps up to 25 years, if the couplings could be dispensed with.
One proposal for dealing with this problem has been to weld tubulars together. However, this is extremely hazardous at the head of an oil or gas well. Furthermore, normal manual welding does not result in a homogeneous metallurgical structure and the corrosion problem remains.
A technique of joining metal components known as "amorphous bonding" has been successfully utilised in the automotive industry. The surfaces of the components to be joined are ground into parallism. A foil of a metal alloy is then placed between the components which are mechanically pressed together. The joint is then subjected to local heating by an induction heater. The resulting structure is nearly metallurgically homogeneous.
It will be appreciated that it would be extremely desirable to be able to join tubulars by amorphous bonding. However, the technical difficulties are daunting insofar as it is necessary to transfer a process suited to a precision engineering shop to an area where inflammable and often explosive gas mixtures are present and where the rigidity of an engineering shop floor is replaced by a drilling platform which may well be offshore and which may be in continuous motion in heavy seas and inclement weather.
It is observed that UK patent specification No. 540,519 discloses a welding device comprising a ring burner which is surrounded by an annular water cooling jacket to reduce explosion hazards during the welding process.
European patent application No. 157131 discloses a double chambered sealing system for welding pipe end which injects inert shield gas in radial and axial directions into unsealed areas around the welding zone to prevent air contamination of said zone.
European patent application No. 418606 discloses an amorphous bonding apparatus in which nitrogen shield gas is injected into a jacket surrounding the bonded tubular ends and also nitrogen gas is injected into the interior of the bonded tubulars to create a virtually oxygen free atmosphere in the region of the bond.
Although the known devices provide some protection against explosion hazards they do not provide sufficient protection in an hazardous environment at the head of an oil or gas well.
The present invention is primarily concerned with reducing the risk of explosion while the amorphous bonding is taking place.